<header>
    两向量的向量积
</header>
<p>
    <span class="title">
        定义
    </span>
    两个向量<code>["vector","a"]</code>和<code>["vector","b"]</code>的向量积（也称外积），记做
    <code>["vector","a"]</code>×<code>["vector","b"]</code>或
    [<code>["vector","a"]</code><code>["vector","b"]</code>]，它的模是
    <span class="oneline">
        |<code>["vector","a"]</code>×<code>["vector","b"]</code>| =
        |<code>["vector","a"]</code>||<code>["vector","b"]</code>|
        sin∠(<code>["vector","a"]</code>,<code>["vector","b"]</code>)
    </span>
    它的方向与<code>["vector","a"]</code>和<code>["vector","b"]</code>都垂直，并且按
    <code>["vector","a"]</code>,<code>["vector","b"]</code>,<code>["vector","a"]</code>×<code>["vector","b"]</code>这个顺序构成右手标架。
</p>
<h2>
    一些相关定理
</h2>
<p>
    <span class="title">
        定理
    </span>
    设<code>["vector","a"]</code>=
    x1<code>["vector","i"]</code> +
    y1<code>["vector","j"]</code> +
    z1<code>["vector","k"]</code>，
    <code>["vector","b"]</code>=
    x2<code>["vector","i"]</code> +
    y2<code>["vector","j"]</code> +
    z2<code>["vector","k"]</code>，
    那么
    <span class="oneline">
        <code>["vector","a"]</code>×<code>["vector","b"]</code> =
        <code>
            ["matrix",[
                [["vector","i"],["vector","j"],["vector","k"]],
                ["x1","y1","z1"],
                ["x2","y2","z2"]
            ],true]
        </code>
    </span>
</p>